74 SEAWEEDS 
among the adjacent cells. There is no division of 
the original cell into pedicel-cell and sporangium. 
When the sporangium reaches its full size the con- 
tents are simultaneously divided into zoospores, which 
do not wholly fill the interior. These escape by the 
rupture of the wall at the apex, and their active 
motion has been observed by Mr. R. M. Laing. 
They are from 500 to 600 in number in each spor- 
angium, and are of the same size as the antherozoids 
of Fucacew and the zoospores of the Laminariacee, 
which latter are formed in similar sporangia. The 
number of sporangia in each conceptacle increases 
with age, and they appear to crowd out, as it were, the 
paraphyses, of which only a few are seen among the 
sporangia at the base of a mature conceptacle. They 
remain, however, in considerable numbers surround- 
ing the mouth. The empty sporangia persist, unlike 
the oogonia of the Fucacee in a similar situation. 
This remarkable plant was included among the 
Fucacee until it was placed apart in its present 
position on its true nature being disclosed by the 
admirable investigation of Miss Margaret Mitchell 
and Miss Frances Whitting.! Its nearest known 
allies are undoubtedly the Laminariacew, from 
which it differs mainly in the sorus of sporangia 
being enclosed within a conceptacle and thus definitely 
limited, and by its remarkable apical cell. 
Its geographical range is in the southern ocean, 
where it is found at the Cape of Good Hope, 
Australia, New Zealand, Seal Island, &c. 
1 Murray’s Phycological Memoirs, part i. 1892, 
